Matheus Carnevali P B, Rohrssen M, Williams M R, Michaud A B, Adams H, Berisford D, Love G D, Priscu J C, Rassuchine O, Hand K P, Murray A E
Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV, USA; Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA.
Geobiology. 2015 Mar;13(2):181-97. doi: 10.1111/gbi.12124. Epub 2015 Jan 22.
The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH4 as a greenhouse gas, the contribution of biogenic CH4 production in arctic thermokarst lakes in Alaska is not currently well understood. To further advance our knowledge of CH4 dynamics in these lakes, we focused our study on (i) the potential for microbial CH4 production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH4 production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in Siqlukaq Lake and two sites in Sukok Lake in late October to early November. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH4 production experiments, and copy number of a methanogenic pathway-specific gene (mcrA) indicated the existence of different sources of CH4 in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH4 production in Siqlukaq at moderate levels, while the very low levels of CH4 detected in Sukok had a mixed origin, with little to no biological CH4 production. Furthermore, methanogenic archaea exhibited temperature-dependent use of in situ substrates for methanogenesis, and the amount of CH4 produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH4 from thermokarst lakes on the coastal plain of Alaska to the current CH4 budgets.
阿拉斯加北坡的永久冻土上分布着大量因热喀斯特侵蚀形成的浅湖。这些湖泊释放的甲烷（CH₄）源于古代热成因气藏和当代生物成因的共同作用。尽管CH₄作为一种温室气体具有潜在的重要性，但目前阿拉斯加北极热喀斯特湖泊中生物成因CH₄的贡献尚不清楚。为了进一步深入了解这些湖泊中CH₄的动态变化，我们的研究集中在以下几个方面：（i）湖泊沉积物中微生物产生CH₄的潜力；（ii）沉积物地球化学在控制生物成因CH₄产生中的作用；（iii）该过程对温度的依赖性。10月下旬至11月初，我们从锡库卡克湖的一个地点和苏科克湖的两个地点采集了沉积物岩芯。对孔隙水地球化学、沉积有机质和脂质生物标志物、稳定碳同位素、CH₄产生实验结果以及产甲烷途径特异性基因（mcrA）的拷贝数进行分析后发现，在所选研究的每个湖泊中都存在不同的CH₄来源。对这一综合数据集的分析表明，锡库卡克湖存在中等水平的生物成因CH₄产生，而在苏科克湖检测到的极低水平的CH₄来源混合，几乎没有生物成因CH₄产生。此外，产甲烷古菌对原位底物的利用表现出温度依赖性，产生的CH₄量与沉积物中不稳定有机质的量直接相关。这项研究是朝着更好地理解阿拉斯加沿海平原热喀斯特湖泊中生物成因CH₄对当前CH₄预算的实际贡献迈出的重要第一步。
